Noninvasive blood pressure measurements are performed by means of corresponding devices and processes and have been known in many variants. For example, EP 0 029 166 B1 describes an electronic blood pressure-measuring device that has a circuit for processing the measured signals.
The prior-art processes and devices are based on the separation of a quasi static signal from a superimposed dynamic signal by means of analog electronic components in suitable evaluating circuits.
In the idealized case, the quasi static signal is a step function decreasing especially over time, which reproduces the currently present pressure preset in the inflatable cuff. The medical measured value that is actually of interest can be determined only from the superimposed dynamic signal.
The separation of the two signals is usually performed in prior-art measuring and evaluating devices via analog filter elements, which have an operational amplifier connected as a high-pass filter with a downstream analog-digital converter.
One essential drawback of the prior-art devices is the dead times of up to 150 msec occurring during measurement in the case of a reduction of the pressure in the cuff by one pressure stage each.